VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 713 



By the foregoing properties the cancerous virus is distinguished from common 

 pus : for when dilute vitriolic acid is added to common pus, no effervescence is 

 produced ; and when a solution of nitrated silver is dropped into this substance 

 previously diffused through distilled water, the mixture does not acquire a brown 

 colour ; nor does any sensible precipitation take place for several hours. It ap- 

 peared however, that when the last experiment was repeated with matter obtained 

 from a venereal bubo, the mixture on the addition of the nitrated silver became 

 slightly turbid, and, at the end of 2 hours, it acquired a brownish cast. The 

 same effects were perceived when the trial was made with matter obtained from a 

 carious bone. But in these instances the precipitation was much less considera- 

 ble than that which was produced by the cancerous matter. 



Dr. C. next endeavoured to procure, in its separate state, a portion of the air 

 which is extricated from the matter of cancer by the vitriolic acid. WitJi this in- 

 tention a quantity of reddish cancerous matter was mixed in a small proof, with 

 about thrice its weight of distilled water. To this mixture a little vitriolic acid 

 was added; on which an effervescence took place, and the air that was disengaged 

 was received in a phial over mercury. When one half of the mercury was ex- 

 pelled from the phial, the latter was inverted over distilled water, and the portion 

 of the mercury that remained in it being suffered to descend, and the water to rise 

 into its place, the phial was closely corked. The air and water were then briskly 

 agitated together, and the phial being a 2d time inverted over distilled water, the 

 cork was removed ; when it appeared by the height to which the water rose, 

 that a part of the air had been absorbed. The water contained in the phial was 

 now found to be strongly impregnated with the odour of the cancerous matter, 

 and a little nitrated silver being dropped into it, a purplish cloud, inclining to red, 

 was produced. It is proper to observe, that the change of colour on the addition 

 of the nitrated silver, in this experiment, was at first scarcely perceptible ; but in 

 the course of a few minutes it became very distinct. As it might perhaps be 

 doubtful, whether this alteration would not be produced in the nitrated silver by 

 exposure to the air alone, the colour of the mixture was compared with that of a 

 similar mixture of nitrated silver and of pure distilled water, which had remained 

 exposed to the open air for an equal length of time. Though a slight change of 

 colour was produced in the latter instance, yet it was much less considerable than 

 that which took place in the former. In the above recited experiment, the air 

 came over mixed with the common air that was contained in the proof. The 

 quantity of aerial fluid that can be thus extricated by the addition of the acid 

 without the assistance of heat, is not very considerable. If heat be applied, a 

 larger portion of fetid air, having the odour of cancerous matter, may be dis- 

 engaged ; but in that case it will be found to be mixed with vitriolic acid air. 

 With a view to obtain the former of these fluids in as pure a state as possible, 



VOL. XVI. 4 Y 



